MULTISTAGE AMPLIFIER TOPOLOGIES WITH NESTED G(M)-C COMPENSATION

This paper presents a multistage amplifier for low-voltage application s (<2 V), The amplifier consists of simple (noncascode) low gain stage s and is stabilized using a nested transconductance-capacitance compen sation (NGCC) scheme, The resulting topology is similar to the well kn own nested Miller compensation (NMC) multistage amplifier, except that the proposed topology contains extra G(m) feedforward stages which ar e used to enhance the amplifier performance. The NGCC simplifies the t ransfer function of the proposed multistage amplifier which, in turn, simplifies its stability conditions, A comparison between the NGCC and NMC shows that the NGCC has wider bandwidth and is easier to stabiliz e. A four-stage NGCC amplifier has been fabricated using a 2-mu m CMOS process and is tested using a +/-1.0 V power supply. A de gain of 100 dB has been measured, A gain bandwidth product of 1 MHz with 58 degre es of phase margin and power of 1.3 mW can be achieved, The op amp occ upies an active area of 0.22 mm(2), Step response shows that the op am p is stable.